Detroit Diesel Fault Codes — Complete Guide

Detroit Diesel SPN/FMI codes cover DD13, DD15, DD16 and 1 more platforms. This hub lists 54 diagnostic pages with symptoms, ranked causes, scan-tool steps, and 2026 repair costs — use INSITE, DiagnosticLink, or EST depending on your engine family.

By Professional Diesel Repair TeamPublished: January 2026Last updated: September 2026

How We Tested and Verified

Detroit Diesel fault code definitions cross-checked against SAE J1939-71 and Detroit Diesel OEM service bulletins. Diagnostic tips validated by field technicians September 2026.

Detroit Diesel Engine Platforms

Detroit Diesel engines covered on this site include: DD13, DD15, DD16, Series 60. Diagnostic procedures vary by platform — always verify against your specific engine serial number and calibration.

Most Common Detroit Diesel Fault Codes

Code	Component	Severity	Definition
SPN 100 FMI 1	Engine Oil Pressure Sensor	Critical	Engine Oil Pressure - Data Valid But Below Normal Operational Range - Most Severe Level
SPN 111 FMI 1	Engine Coolant Level Sensor	Critical	Engine Coolant Level - Data Valid But Below Normal Operational Range - Most Severe Level
SPN 1569 FMI 31	Engine Protection Torque Derate	Critical	Engine Protection System - Torque Derate - Condition Exists
SPN 157 FMI 4	Injector Metering Rail 1 Pressure	Critical	Injector Metering Rail 1 Pressure - Voltage Below Normal (FMI 4)
SPN 175 FMI 0	Engine Oil Temperature Sensor	Critical	Engine Oil Temperature 1 - Data Valid But Above Normal Operational Range - Most Severe Level
SPN 3226 FMI 13	Outlet NOx Sensor	Critical	Selective Catalytic Reduction NOx Efficiency Low - Out of Calibration
SPN 4363 FMI 0	SCR Outlet Gas Temperature Sensor	Critical	Aftertreatment 1 SCR Catalyst Outlet Gas Temperature - Data Valid But Above Normal Operational Range - Most Severe Level
SPN 5246 FMI 16	SCR Inducement	Critical	Aftertreatment SCR Operator Inducement - Data Valid But Above Normal Operating Range - Severe
SPN DD15-ONEBOX FMI N/A	Detroit DD15 One-Box Aftertreatment	High	Common failure patterns on Detroit DD15 One-Box aftertreatment — DPF, DOC, SCR catalyst, and DEF dosing faults diagnosed with DDDL
SPN DDDL-SCR FMI N/A	Detroit DDDL SCR Derate Diagnostics	High	How to use Detroit Diesel Diagnostic Link (DDDL) to diagnose SCR derate, inducement stages, and aftertreatment faults on DD13, DD15, and DD16 engines
SPN 100 FMI 17	Engine Oil Pressure	High	Engine Oil Pressure - Data Valid But Below Normal Operational Range - Least Severe Level
SPN 100 FMI 2	Engine Oil Pressure Sensor / Oil Pressure Circuit	High	Engine Oil Pressure - Data Erratic, Intermittent, or Incorrect
SPN 1322 FMI 31	Multiple Cylinder Misfire Detection	High	Engine Misfire for Multiple Cylinders - Condition Exists
SPN 1382 FMI 16	Fuel Filter Differential Pressure Sensor	High	Fuel Filter Differential Pressure - Data Valid But Above Normal Operating Range - Moderately Severe Level
SPN 1761 FMI 18	DEF Tank Level Sensor	High	Aftertreatment 1 Diesel Exhaust Fluid Tank Level - Data Valid But Below Normal Operating Range - Moderately Severe Level
SPN 2789 FMI 14	VGT Actuator Position	High	Turbocharger 1 Variable Geometry Actuator - Special Instruction (Commanded Position Not Reached)
SPN 3031 FMI 10	EGR Valve	High	Engine Exhaust Gas Recirculation Valve - Abnormal Rate of Change
SPN 3216 FMI 0	SCR Intake NOx Sensor	High	Aftertreatment SCR Intake NOx Sensor - Data Valid But High
SPN 3226 FMI 0	SCR Outlet NOx Sensor	High	Aftertreatment SCR Outlet NOx Sensor - Data Valid But Above Normal Operating Range
SPN 3242 FMI 1	DPF Intake Gas Temperature Sensor	High	Aftertreatment 1 Diesel Particulate Filter Intake Gas Temperature - Data Valid But Below Normal Operating Range

Detroit Diesel-Specific Diagnostic Tips

Detroit DiagnosticLink shows One-Box aftertreatment efficiency in real time.
Outlet NOx sensor drift is common after DEF crystallization — clean doser before sensor swap.
DD15 oil pressure at hot idle should read 25–35 PSI; below 20 PSI risks SPN 100 protection.